Javascript，Jquery Validator插件，ajax - 带回调的异步替换

I'm beginner at javascript so learning constantly very many new things so dont be angry if im asking a really stupid question because still learing the ropes. Trying to implement callback instead async: false. Adding this method to jquery Validator plugin. With async false works fine, but i don't wanna use it. Any help appreciated :)I'm beginner at javascript so learning constant